Check out this article from ACRES USA June 2015 edition. Worm Castings are ideal for sowing time. They are rich in phosphorous which stimulates seedling and root growth and extension.
Did you know conventional fertilisers suppress root growth?
Worm Castings also have the trifecta of available calcium, carbon and nitrate, they neutralize the soil, totally sidestepping the ammonia toxicity and salt issues common in ammonia rich fertilisers.